draft-ietf-tcpm-rto-consider-00.txt   draft-ietf-tcpm-rto-consider-01.txt 
Internet Engineering Task Force M. Allman Internet Engineering Task Force M. Allman
INTERNET-DRAFT ICSI INTERNET-DRAFT ICSI
File: draft-ietf-tcpm-rto-consider-00.txt February 2, 2016 File: draft-ietf-tcpm-rto-consider-01.txt February 29, 2016
Intended Status: Best Current Practice Intended Status: Best Current Practice
Expires: August 2, 2016 Expires: August 29, 2016
Retransmission Timeout Considerations Retransmission Timeout Considerations
Status of this Memo Status of this Memo
This document may not be modified, and derivative works of it may This document may not be modified, and derivative works of it may
not be created, except to format it for publication as an RFC or to not be created, except to format it for publication as an RFC or to
translate it into languages other than English. translate it into languages other than English.
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 5, line 14 skipping to change at page 5, line 14
(4) Retransmission timeouts MUST be taken as indications of (4) Retransmission timeouts MUST be taken as indications of
congestion in the network and the sending rate adapted using a congestion in the network and the sending rate adapted using a
standard mechanism (e.g., TCP collapses the congestion window to standard mechanism (e.g., TCP collapses the congestion window to
one segment [RFC5681]). one segment [RFC5681]).
This ensures network safety. This ensures network safety.
An exception is made to this rule if a standard mechanism is An exception is made to this rule if a standard mechanism is
used to determine that a particular loss is due to a used to determine that a particular loss is due to a
non-congestion event (e.g., bit errors or packet reordering). non-congestion event (e.g., packet corruption). In such a case
In such a case a congestion control action is not required. a congestion control action is not required. Additionally,
RTO-triggered congestion control actions may be reversed when a
standard mechanism determines that the cause of the loss was not
congestion after all.
3 Discussion 3 Discussion
We note that research has shown the tension between responsiveness We note that research has shown the tension between responsiveness
and correctness of TCP's RTO seems to be a fundamental tradeoff and correctness of TCP's RTO seems to be a fundamental tradeoff
[AP99]. That is, making TCP's RTO more aggressive (via the EWMA [AP99]. That is, making TCP's RTO more aggressive (via the EWMA
gains, lowering the minimum RTO, etc.) can reduce the time spent gains, lowering the minimum RTO, etc.) can reduce the time spent
waiting on needed retransmissions. However, at the same time such waiting on needed retransmissions. However, at the same time such
aggressiveness leads to more needless retransmissions, as well. aggressiveness leads to more needless retransmissions, as well.
Therefore, being as aggressive as the guidelines sketched in the Therefore, being as aggressive as the guidelines sketched in the
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